1. Field of the Invention
The present invention relates to controlling a pedometer based on the use of inertial sensors.
2. Description of the Related Art
As is known, a pedometer is a device that can be carried by a user and has the function of counting the number of steps during various walking or running activities for estimating accordingly the distance traveled. The indications supplied are useful for quantifying the motor activity performed by a person in the course of a given period, for instance, for clinical purposes, for assessing the athletic performance, or even just for simple personal interest.
The reliability of a pedometer obviously depends on the precision in estimating the step length of the user at the various rates of locomotion, but also on the selectivity in recognizing and ignoring events not correlated to the gait, which, however, cause perturbations resembling those produced by a step. For example, many pedometers are based on the use of inertial sensors, which detect accelerations along a substantially vertical axis, and recognize that a step has been being made by a user when the time plot of the acceleration signal shows given morphological characteristics. Basically, a step is recognized when the pedometer detects a positive acceleration peak (i.e., a peak directed upwards) having an amplitude greater than a first threshold, followed, at a distance of some tenths of second, by a negative acceleration peak (directed downwards) having an amplitude greater than a second threshold. However, there are many random events that can interfere with correct recognition of the step. Impact or other external vibrations and given movements of the user can, in fact, give rise to so-called “false positives”, i.e., to events that are recognized as steps even though in actual fact they are not, because the morphological characteristics produced are compatible. Events of this type are very frequent also in periods of rest, when the user, albeit not walking, in any case performs movements that can be detected by the pedometer. In the majority of cases, also “isolated” steps or very brief sequences of steps are far from significant and should preferably be ignored because they are, in effect, irrelevant in regard to assessment of the motor activity for which the pedometer is being used.
Of course, in all these situations, the count of the steps may prove to be completely erroneous.